Comparative transcriptomic analysis reveals genetic factors underlying susceptibility of largemouth bass to the complex stress elicited by transportation

Abstract

Live fish transportation is a common practice in aquaculture, but it can cause complex stress and lead to decreased immunity and mass mortality. However, the genetic mechanisms determining fish resistance to transportation stress are not well understood. In this study, largemouth bass (Micropterus salmoides) juveniles were transported by car for 4 hours, resulting in a mortality rate of 33.61 ± 10.58 % during recovery. Except for the dead ones, stress-sensitive individuals with abnormal symptoms were identified, showing significantly lower levels of glutathione and superoxide dismutase in their livers compared to normal individuals (p < 0.05). RNA sequencing of liver and spleen samples collected before transportation (T0), at the end of transportation (Te), and after 1, 3, 4 and 5 days of recovery (R1d, R3d, R4d and R5d) revealed transcriptional responses to the stress. Up-regulated genes in the liver were associated with cholesterol, sterol and steroid biosynthesis, while those in the spleen were related to hemopoiesis and immune response. Down-regulated genes in both tissues were linked to neurogenesis, angiogenesis and cell migration. Analysis of differentially expressed genes between normal and abnormal fish suggested that failure to terminate stress responses and organ function depression may contribute to stress susceptibility. Core genes associated with stress susceptibility were enriched in glycolysis. These findings shed light on the genetic factors influencing largemouth bass’s susceptibility to transportation stress.